Contamination by microorganisms is one of the most troublesome problems encountered in hospitals and clinics today and there is often a need to sterilize devices such as medical instruments and the like. In particular, the rapid succession of medical examinations of patients called for by modern methods of clinical health practice requires continuous sterilization of numerous devices in succession; this is particular true with endoscope devices.
In U.S. Pat. Nos. 4,169,123 and 4,169,124 cold gas sterilization using hydrogen peroxide gas at temperatures below 80.degree. C. is disclosed. The liquid hydrogen peroxide is vaporized and the hydrogen peroxide vapor is then introduced into the sterilization chamber by pressure differential.
U.S. Pat. No. 4,642,165 discloses a method of injecting and vaporizing successive increments of a multicomponent liquid such as an aqueous solution of hydrogen peroxide, for delivery into a vacuum chamber. The vacuum in the chamber draws the multicomponent vapor into the chamber.
U.S. Pat. No. 4,512,951 discloses a method of liquid contact hydrogen peroxide sterilization. Goods to be sterilized are maintained in the sterilization chamber at a temperature below the dew point of the vapor sterilant. An aqueous solution of hydrogen peroxide is vaporized and passed into the evacuated sterilization chamber were, upon contact with the goods, the vapor condenses to form a liquid layer of sterilant on the goods. A vacuum in the chamber draws the vapor into the chamber.
United Kingdom Patent No. 1,582,060 discloses a similar liquid contact hydrogen peroxide sterilization method operated without a vacuum chamber. Liquid hydrogen peroxide is pumped through an ultrasonic spray nozzle which is operated by a stream of dehydrated air. A mist of hydrogen peroxide is sprayed into a container and mixed with hot air to change the mist into a vapor. The vapor is piped into a non-pressurized sterilization chamber where it condenses on a cool moving web of material. A stream of hot air in an adjacent chamber removes the hydrogen peroxide layer from the web. The stream is then passed to a water separator where it is relieved of the sterilant.
U.S. patent application Ser. No.07/851,096, incorporated by reference herewith, discloses the use of a sealable cassette in which the endoscope or other object is placed. The cassette has input and output fluid sealing ports for the introduction and removal of sterilizing fluid. The endoscope or other medical instrument, if hollow, is coupled with to the input or output port. The cassette is formed of two identical halves which are placed in superimposed sealable relationship with each other to form a hollow chamber. A latch is placed on one or more handles on the cassette to create a pre-sealing condition to allow a vacuum to be introduced at the outlet part.
The cassette is then placed in an outer-oven-like container or warming chamber or cabinet where the temperature is properly maintained. Connections are made to open the input and output ports on the cassette such that the sterilizing agent may be introduced through a first port to bathe the outside of the medical instrument or other object, such as an endoscope, while one end of the hollow object, such as an endoscope, is coupled to the output port where a vacuum is supplied external to the cassette to pull the sterilization agent into the cassette and through the interior passage ways of the hollow object.
U.S. patent application Ser. No. 07/851,096, further teaches a system for sterilizing an object comprising a hollow cassette for containing the object, the cassette having an opening section for ingress and egress of the object, sealing means for forming a fluid-tight seal around the opening section, input and output ports in the cassette for receiving and exhausting a sterilizing fluid, and a sealing check valve in the input and output ports for providing a fluid-tight seal when connections are made to the input and output ports such that when the object is sterilized within the cassette, the cassette will maintain a sterilized atmosphere for the object until the cassette is opened to allow use of the object.
It is necessary to know the temperature within the casing or holding cassette to insure optimum sterilization. Current methods of temperature measurement using the cassette and system described U.S. patent Application Ser. No.07/851,096, include having a temperature sensor connected directly to either the object to be sterilized or the casing or cassette holding the object. The temperature sensor or associated wiring is attached to the holding cassette at each use and then disconnected. This level of handling is inconvenient and provides an increased opportunity for damage to the sensor.
Additionally, if vapor sterilant is used to sterilize the particular object (e.g. endoscopes, steel or plastic light guides, scissors, hemostats, camera cords etc.) it is not only desirable to know the internal temperature of the holding cassette so that the sterilant can be introduced thereto at the appropriate temperature to optimize the partial pressure of the sterilant in the gas, thereby optimizing the kill rate, but it is also desirable to know the internal temperature of the cassette with respect to the surrounding environment to prevent condensation of moisture in the air within the cassette. It is important to avoid having sterilant vapor condense onto the particular object to be sterilized or on the walls of the cassette in order to insure the proper level of sterilization and to avoid any degradation that may take place by a liquid sterilant contacting the cassette or object contained therein.
There is a need for a method which can measure the temperature of an object in a remote manner such that direct contact with the sensing device and the object, casing or holding cassette is not necessary and while providing accurate knowledge of the internal temperature.